In recent years, for a purpose of environmental protection and the like, an electric motorcycle in which an electric motor to be driven by electric energy stored in a battery is used as a traveling power source has been developed (for example, refer to Patent Document 1). The electric motor of Patent Document 1 is arranged on the same axis as that of a rear wheel adjacently to the left side of the rear wheel, so that rotation of an output shaft of the electric motor is directly transmitted to the rear wheel.